In Dallas, you can hold up to two garage sales a year.  No permit is required.  Some additional restrictions:

• A person shall sell tangible personal property only on the premises of the owner or lessee of the premises where the sale is conducted, and the owner or lessee must be the legal owner of the tangible personal property at the time of the sale.
• The sale must be inside the building or garage, or on the patio of the premises
• A person shall not sell, offer, or advertise for sale merchandise made, produced, or acquired solely for the purpose of resale at an occasional sale
• A person shall not conduct an occasional sale for a duration of more than three consecutive calendar days
• A person shall not conduct more than two occasional sales at a premises during any 12 month period
• A person shall not place more than one sign, not to exceed two square feet, upon the lot where the sale is taking place. Any other signs at any locations remote from the sale property are not permitted
• The area restrictions in the general provisions do not apply to this use
• Any advertisement of an occasional sale or of an item being offered for sale at an occasional sale must contain the street address at which the sale will occur and the date(s) on which the sale will occur